1. Field of the Invention
The present invention relates to the field of passive solar energy heating units which may be installed in building walls in the manner of windows.
2. Description of the Related Art
Passive solar heating units of the subject type are known in the art. For example, U.S. Pat. No. 4,532,917 to Taff et al. shows a modular passive solar energy heating unit for heating an enclosed space. The unit employs phase change heat storage material, which is optically transparent to visible light when in a high-stored-energy liquid state, enabling a viewer to see through clearly, and which is translucent milky white when in a low-stored-energy solid state for providing pleasant illumination to the enclosed space when first illuminated by sunlight in the morning.
An undesirable characteristic of this and other such modular passive solar energy heating units of the prior art is their tendency to radiate too much of the heat stored during the daylight hours back outside the building at night. As a consequence, less of the stored heat remains available to heat the building at night. In addition, the heat that does remain to be transmitted into the building does so too quickly, with the result that its benefit is felt for only a relatively short time.
The present invention provides a solution to these and other problems of the prior art.